Locomotive air compressor system with enhanced protection against leakage causative of backflow of pressurized air from a reservoir

ABSTRACT

A compressor system, method and kit are provided for supplying pressurized air to a main storage reservoir of a locomotive. The compressor system includes a high-pressure cylinder having at least one outlet valve having a first set of sealing characteristics. The compressor system further includes a piping assembly connected to the outlet valve to selectively pass pressurized air to the reservoir. The piping assembly may comprise a T-fit coupler connected to first and second pipes for delivering the pressurized air to the reservoir. A check valve may be installed in a chamber defined in the T-fit coupler. The check valve has a second set of sealing characteristics different than the sealing characteristics of the outlet valve. The check valve is responsive to predefined operational conditions of the air compressor system so that when the compressor system is supplying pressurizing air to the reservoir the check valve is set to an open condition. When the compressor system stops supplying pressurizing air to the reservoir, the check valve is set to a closed condition. The combined sealing characteristics of the outlet valve and the check valve is chosen to limit backflow of pressurized air from the reservoir to the high pressure cylinder.

This application claims the benefit of U.S. application Ser. No. 60/587,448, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention is directed to air compressor systems for railroad locomotives, and, more particularly, to an air compressor system with enhanced protection against leakage that may cause backflow of pressurized air from a reservoir.

BACKGROUND OF THE INVENTION

It is known to use multi-cylinder air compressors on freight and passenger locomotives to supply compressed air to a main storage reservoir and in turn to various locomotive systems, such as the operating and control equipment of a railway air brake system.

One issue that has affected such compressor systems may arise due to leakage of pressurized air from the main storage reservoir into a high-pressure cylinder of the compressor system. This can cause a buildup of pressure in the high-pressure cylinder that must be overcome by a rotatable prime mover (e.g., electric motor) of the air compressor system. That is, the compressor motor may be forced to supply a relative high level of starting torque in order to overcome the buildup of backpressure in the high-pressure cylinder. This is undesirable because this can detrimentally affect the expected life of the motor and can lead to premature wear and tear and malfunctions of various mechanical, electrical or electromechanical components of the air compressor system.

One known technique that has been used for reducing the possibility of performing hard motor starts may entail time-consuming and burdensome operations. For example, this known technique may require the following operations: access to the piping connected to the inlet valves of the high-pressure cylinder, connecting a pressure source to pressurize the piping. The pressurization level is selected sufficiently high to cause opening of the inlet valves of the high cylinder so that the buildup of pressure in the high cylinder passes through those open valves and through the piping connected to those valves to be eventually vented to the surrounding environment at an appropriate outlet. It will be appreciated that the foregoing technique (leaving aside the incremental burdens required for performing it) for reducing the possibility of hard motor starts is just a partial solution since that technique does not address the loss of pressurized air that occurs from the main storage reservoir to the high pressure cylinder in the event a leakage condition develops at the outlet valves of the high pressure cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which:

FIG. 1 illustrates a schematic representation of an exemplary locomotive air compressor system embodying aspects of the present invention.

FIG. 2 schematically illustrates an exemplary piping assembly for providing a pneumatic connection between a pair of outlet valves in the high pressure cylinder of the air compressor system of FIG. 1 and a main storage reservoir.

FIG. 3 illustrates a sectional view of respective spring-loaded inlet and outlet valves in a high-pressure cylinder of the air compressor system of FIG. 1.

FIGS. 4A and 4B respectively illustrate open and closed conditions of a valve, such as a ball check valve, having a set of sealing characteristics different than the sealing characteristics of the valves illustrated in FIG. 3.

FIGS. 5A and 5B respectively illustrate open and closed conditions of a valve, such as a swing check valve, having a set of sealing characteristics different than the sealing characteristics of the valves illustrated in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a locomotive air compressor system 10 that in one exemplary embodiment comprises a multi-cylinder, two-stage, air-cooled compressor. A first stage (e.g., a low-pressure stage) includes a first low-pressure cylinder 20 and a second low-pressure cylinder 22. A second stage (e.g., a relatively high pressure stage) includes a high-pressure cylinder 24. Each of such cylinders may be provided with cooling fins. As shown, the pair of low pressure cylinders 20 and 22 and the high pressure cylinder 24 may be mounted on and supported by a crankcase 26 in the usual manner and include respective pistons which are actuated by connecting rods driven by a rotatable crankshaft 28. One end of the crankshaft 28 may be coupled to and driven by a suitable rotatable prime mover, such as an electric motor (not shown), while the other end of the crankshaft 28 may be attached to a rotary cooling fan assembly 29.

Each low-pressure cylinder includes a pair of inlet valves 30. A pair of outlet valves 40 of the low-pressure cylinder 20 (only one shown) may be connected to an inlet header of a first intercooler 12. Typically, the valves may be spring-loaded valves responsive to negative or positive pressure to reach either a closed or an open condition.

An outlet header of intercooler 12 is connected to one inlet of a T-pipe fitting 44. Similarly, a pair of outlet valves 46 of the low-pressure cylinder 22 is connected to an inlet header of a second intercooler 14 via a pipe 48. An outlet header of intercooler 14 is connected to the other inlet of the T-pipe fitting 44, while the outlet of the T-pipe fitting 44 is connected to a pair of inlet valves 50 of the high-pressure cylinder 24. A pair of outlet valves 52 of the high pressure cylinder 24 is connected by way of a T-pipe fitting 54 and a pair of conduits 56 ₁ and 56 ₂ to the inlets of a main storage reservoir 58 (FIG. 2). In one exemplary embodiment, conduit 56 ₁ may be directly connected to the main storage reservoir while conduit 56 ₂ may be connected through a heat exchanger (not shown).

In operation, once the main storage reservoir has been pressurized to a desired pressure level and the compressor system is in an “off” or “unloaded” state, outlet valves 52 in theory should fully close so that there is no further flow communication between the main storage reservoir and the high-pressure cylinder. In practice, however, it has been observed that outlet valves 52 often fail to provide an appropriate sealing function relative to the main storage reservoir. As illustrated in FIG. 3, each inlet and outlet valve 50 and 52 of the high-pressure cylinder 24 comprises spring-loaded valves responsive to negative or positive pressure to reach either a closed or an open condition. In operation, the environment within the high-pressure cylinder head may, for example, contain oil residues that may lead to buildup of oil debris and detrimentally affect the sealing function of the valves therein. Also the spring-load characteristics of the valves may be affected, for example, due to wear and tear and this can also detrimentally affect the sealing function of the valves in the high-pressure cylinder.

More particularly, the tendency to leak of outlet valves 52 can lead to undesirable backflow of pressurized air from the main storage reservoir into the high-pressure cylinder. The leakage of pressurized air from the main storage reservoir can cause the pressurization of that reservoir to fall below a desired pressure level, and this in turn can lead to incremental running of the air compressor system to compensate for such a loss of pressurized air, thereby causing unnecessary additional operational costs and incremental wear and tear to the air compressor system. Moreover, during a subsequent start of the compressor system, the leakage of pressurized air from the main storage reservoir into the high-pressure cylinder 24 can cause a buildup of pressure in the high-pressure cylinder that must be overcome by the rotatable prime mover of the air compressor system.

The inventors of the present invention have recognized an innovative improvement that addresses the foregoing issues without having to undertake any expensive and time-consuming redesign of the air compressor system. More particularly, the present inventors have recognized that the interior of the T-pipe fitting 54 may be used for accommodating a check valve 60 responsive (e.g., mechanically responsive) to operational conditions of the air compressor system to reach either a fully closed or a fully open condition.

For example, when the air compressor system is in an “on” or a “loaded” condition (e.g., while generating pressurized air), then valve 60 should be in a fully open condition so that flow communication is fully maintained between the high pressure cylinder 24 and the main storage reservoir. Conversely, upon reaching a desired level of pressurization in the main storage reservoir, and the compressor system reaching an “off” or an “unloaded” condition (e.g., stoppage of generating pressurized air), then valve 60 should be in a fully closed condition. In this manner, regardless of any leakage condition that may develop in the outlet valves 52 (only one valve shown in FIG. 2), one can maintain a substantially tight pressure seal between the high-pressure cylinder 24 and the main storage reservoir. Preferably, valve 60 is of another and different construction from that of the spring-loaded relief-type outlet valves in the high-pressure cylinder, so that valve 60 complements the sealing functionality provided by the outlet valves to prevent undesirable reverse direction air flow in the system while at the same time minimizing any addition of friction-induced head loss during normal direction air flow when the compressor is operating. In one exemplary embodiment, valve 60 may comprise a ball check valve, as schematically illustrated in FIGS. 4A and 4B.

The condition illustrated in FIG. 4A corresponds to a condition when the air compressor system is in an “on” (e.g., while generating pressurized air), wherein valve 60 is in a fully open condition so that flow communication is fully maintained between the high-pressure cylinder 24 and the main storage reservoir. Upon reaching a desired level of pressurization in the main storage reservoir, and the compressor system reaching an “off” or an “unloaded” condition (e.g., stoppage of generating pressurized air), then valve 60 is set in a fully closed condition, as illustrated in FIG. 4B. Advantageously, a valve of such design provides the reverse flow isolation capability with a minimal increase in forward flow pressure head loss.

In another exemplary embodiment, valve 60 may comprise a swing check valve, as schematically illustrated in FIGS. 5A and 5B. The condition illustrated in FIG. 5A corresponds to a condition when the air compressor system is in an “on” or a “loaded” condition (e.g., while generating pressurized air), wherein valve 60 is in a fully open condition so that flow communication is fully maintained between the high-pressure cylinder 24 and the main storage reservoir. Upon reaching a desired level of pressurization in the main storage reservoir, and the compressor system reaching an “off” or an “unloaded” condition (e.g., stoppage of generating pressurized air), then valve 60 is set in a fully closed condition, as illustrated in FIG. 5B. As in the example of a ball check valve, a swing check valve provides the reverse flow isolation capability with a minimal increase in forward flow pressure head loss.

It will be now appreciated by those skilled in the art that the sealing functionality provided by check valve 60 (between the high-pressure cylinder and the main storage reservoir) complements the sealing functionality provided by the outlet valves in the high-pressure cylinder with respect to the main storage reservoir. It is noted that in view of the distinct environment for the check valve and the structural and functional differences between the check valve and the outlet valves in the high-pressure cylinder, the incremental sealing functionality provided by added check valve 60 is complementary rather than just duplicative of the functionality provided by the outlet valves in the high-pressure cylinder.

The above-described structural modification is particularly attractive since it lends itself to retrofit operations that, in order to be successful, are generally required to meet the following exemplary criteria: little or no impact to field-deployed hardware; a relatively low-cost impact to the retrofit; user-friendly installation operations that may be performed without expensive equipment and tools and without having to provide any substantial training to service personnel; and essentially being transparent regarding the basic design and functionality of the compressor system (no requirements for having to re-qualify the design of the compressor system). It is believed that the present invention meets the foregoing criteria while providing lower operational costs and providing incrementally higher operational reliability and durability for the air compressor system.

Another exemplary embodiment may utilize a separate check valve for each of the connecting pipes 56. This embodiment may add some redundancies against some possible failure modes. For example, in the event one of the check valves were to become stuck in a closed condition and one of the pipes 56 was no longer in flow communication with the reservoir, then the other check valve and the other pipe would still allow for flow communication from the high pressure cylinder to the reservoir. 

1. A compressor system for supplying pressurized air to a main storage reservoir of a locomotive, said compressor system comprising: a high-pressure cylinder having at least one outlet valve having a first set of sealing characteristics; a piping assembly connected to said outlet valve to selectively pass pressurized air to the reservoir; and a valve disposed in said piping assembly having a second set of sealing characteristics different than the sealing characteristics of the outlet valve, said valve responsive to predefined operational conditions of the air compressor system so that when the compressor system is supplying pressurizing air to said reservoir said valve is set to an open condition, and when said compressor system stops supplying pressurizing air to said reservoir said valve is set to a closed condition, the combined sealing characteristics of the outlet valve and the valve in the piping assembly being chosen to limit backflow of pressurized air from the reservoir to the high pressure cylinder.
 2. The compressor system of claim 1 wherein said piping assembly includes a T-fit coupler connected to first and second pipes for delivering the pressurized air to said reservoir, said T-fit coupler defining a chamber for accommodating said valve.
 3. The compressor system of claim 1 wherein the valve in the piping assembly comprises a check valve selected from the group consisting of a ball check valve and a swing check valve, and the set of sealing characteristics for said outlet valve comprises a spring-load sealing.
 4. A compressor system for supplying pressurized air to a main storage reservoir of a locomotive, said compressor system comprising: a high-pressure cylinder having at least one outlet valve having a first set of sealing characteristics; a piping assembly connected to said outlet valve to selectively pass pressurized air to the reservoir, said piping assembly comprising a T-fit coupler connected to first and second pipes for delivering the pressurized air to said reservoir; and a check valve disposed in a chamber defined in said T-fit coupler, said check valve having a second set of sealing characteristics different than the sealing characteristics of the outlet valve, said check valve responsive to predefined operational conditions of the air compressor system so that when the compressor system is supplying pressurizing air to said reservoir said check valve is set to an open condition, and when said compressor system stops supplying pressurizing air to said reservoir said check valve is set to a closed condition, the combined sealing characteristics of the outlet valve and the check valve being chosen to limit backflow of pressurized air from the reservoir to the high pressure cylinder.
 5. The compressor system of claim 4 wherein said check valve is selected from the group consisting of a ball check valve and a swing check valve, and the set of sealing characteristics for said outlet valve comprises a spring-load sealing.
 6. A method for pneumatically interconnecting a high-pressure cylinder having at least one outlet valve having a first set of sealing characteristics to a main storage reservoir of a locomotive, said method comprising: connecting a piping assembly to said outlet valve to selectively pass pressurized air to the reservoir, said piping assembly comprising a T-fit coupler connected to first and second pipes for delivering the pressurized air to said reservoir; and installing a valve in a chamber defined in said T-fit coupler, said valve having a second set of sealing characteristics different than the sealing characteristics of the outlet valve, the valve in the chamber responsive to predefined operational conditions of the air compressor system so that when the compressor system is supplying pressurizing air to said reservoir said valve is set to an open condition, and when said compressor system stops supplying pressurizing air to said reservoir said valve is set to a closed condition, the combined sealing characteristics of the outlet valve and the valve in the chamber being chosen to limit backflow of pressurized air from the reservoir to the high pressure cylinder.
 7. A kit for a compressor system for supplying pressurized air to a main storage reservoir of a locomotive, said compressor system comprising a high-pressure cylinder having at least one outlet valve having a first set of sealing characteristics, said compressor system further comprising a piping assembly connected to said outlet valve to selectively pass pressurized air to the reservoir, said piping assembly comprising a T-fit coupler connected to first and second pipes for delivering the pressurized air to said reservoir, said kit comprising: a valve to be installed in a chamber defined in said T-fit coupler, said valve having a second set of sealing characteristics different than the sealing characteristics of the outlet valve, said valve responsive to predefined operational conditions of the air compressor system so that when the compressor system is supplying pressurizing air to said reservoir said valve is set to an open condition, and when said compressor system stops supplying pressurizing air to said reservoir said valve is set to a closed condition, the combined sealing characteristics of the outlet valve and the valve to be installed in the chamber being chosen to limit backflow of pressurized air from the reservoir to the high pressure cylinder.
 8. The kit of claim 7 wherein said valve comprises a check valve selected from the group consisting of a ball check valve and a swing check valve, and the set of sealing characteristics for said outlet valve comprises a spring-load sealing. 